1. Field of the Invention
The present invention relates to an optical module used in an optical communication system such as an optical data link or an optical local area network (LAN), which uses light as an information transmission medium.
2. Related Background Art
As optical modules used in an optical communication system, there are a transmission module using a light-activated element such as an LED or a semiconductor laser as an electrooptic converting element (light-emitting element), and a reception module using a light-activated element such as a pin-photodiode as a photoelectric converting element (light-receiving element). Such an optical module generally has a light-activated element such as a light-emitting element or a light-receiving element, electronic components electrically connected to the light-activated element and arranged on a circuit board, a lens system, and a sleeve in which the end portion of an optical fiber is inserted. For an optical fiber with a fiber core having a diameter of several tens .mu.m, the light-activated element, the lens system, and the sleeve must be assembled at high precision. For this reason, an optical module as shown in FIG. 1 is conventionally used.
The optical module shown in FIG. 1 has a cylindrical holding body 1. The holding body 1 is formed of a metal such as stainless steel. A lens (not shown) is arranged in the holding body 1 at one end. The other end portion of the holding body 1 serves as a sleeve for receiving a ferrule (not shown) at the end portion of an optical fiber. A light-activated element 2 is fixed to the holding body 1 with an adhesive or the like. The light-activated element 2 is arranged such that the optical axes of the element 2, the ferrule connected to the holding body 1 and the lens are matched with each other.
The holding body 1 having the light-activated element 2 fixed therein is supported, together with a circuit board 3, by a package main body 4 consisting of a ceramic or metal. The terminals of the light-activated element 2 are connected by soldering (not shown) to electronic components 5 such as bare chip ICs mounted on the circuit board 3.
The package main body 4 has inner lead pins 6 mounted inside the body 4, and outer lead pins 7 mounted outside the body 4 and electrically connected to the inner lead pins 6. The inner lead pins 6 are electrically connected to terminals on the circuit board 3 by soldering. The wiring pattern and the electronic components 5 are sealed by a lid 8. Finally, a cover 9 is fixed to the package main body 4, thereby completing the optical module.
In the conventional optical module as described above, the light-activated element 2 is held by the holding body 1 formed of a metal cylinder. The holding body 1 is an independent member which separates from the package main body 4 having the circuit board 3 mounted thereon and the cover 9. For this reason, there are many components of the module, resulting in higher productive cost and lower productive efficiency.
Although not illustrated, an optical module is known in which a lead frame is used in place of a package main body and a cover. A circuit board and a light-activated element are mounted in the lead frame, and all these components are integrally molded with a plastic (Japanese Utility Model Laid-Open No. 2-126107). In this case, however, the light-activated element and the circuit board are independent members, as in the optical module shown in FIG. 1. Therefore, the same problem as in FIG. 1 is present.